Abstract: For the treatment of contaminated mine waters reliable treatment methods with low investment and operational costs are essential. Therefore, passive treatment systems recently have been installed in Great Britain and in Germany (e.g. anoxic limestone drains, constructed wetlands, reactive barriers, roughing filters) and during the last eight years such systems successfully treated mine waters, using up to 6 ha of space. In some cases with highly contaminated mine water, a combination of active and passive systems should be applied, as in any case the water quality has to reach the limits. Because not all the processes of passive treatment systems are understood in detail, current research projects (e.g. EU-project PIRAMID) were established to clarify open questions.

Abstract: Seven kilometres of the River Pelenna in South Wales were impacted for approximately 30 years by discharges from abandoned coal mines. Elevated iron and low pH caused significant ochreous staining and had detrimental effects on the river ecology. The River Pelenna Mine water project constructed a series of passive wetland treatment systems to treat these discharges. Monitoring of the performance and environmental benefits of these has been undertaken as part of an Environment Agency R&D project. This project has assessed the changes in water quality as well as monitoring populations of invertebrates, fish and birds between 1993 and 2001. Performance data from the wetlands show that on average the three systems are removing between 82 and 95% of the iron loading from the mine waters. In the rivers downstream, the dissolved iron concentration has dropped to below the Environmental Quality Standard (EQS) of 1 mg/L for the majority of the time. Increases in pH downstream of the discharges have also been demonstrated. Trout (Salmo trutta) recovered quickly following mine water treatment, returning the next year to areas that previously had no fish. Intermittent problems with overflows from the treatment systems temporarily depleted the numbers, but the latest data indicate a thriving population. The overflow problems and also background episodes of acidity have affected the recovery of the riverine invertebrates. However, there have been gradual improvements in the catchment, and in the summer of 2001 most sites held faunas which approached those found in unpolluted controls. Recovery of the invertebrate fauna is reflected in marked increases in the breeding success of riverine birds between 1996 and 2001. This study has shown that constructed wetlands can be an effective, low cost and sustainable solution to ecological damage caused by abandoned mine drainage.

Abstract: Der Bruch des Dammes einer Halde der Grube Nr. 14 des Kupfer- Bergbaubetriebes Pinto Valley in Arizona, USA, im Jahre 1997 führte zum Eintrag von 370000 yd(exp 3) Bergematerials und Tailings in das Bett des Flusses Pinto Creek, USA, wodurch letzteres blockiert wurde. Der Vorfall ereignete sich in bergigem Gelände unterhalb eines 14 Quadratmeilen großen Abschnittes des Flusseinzugsgebietes oberhalb des Sees Roosevelt Lake, USA, einer Trinkwasserquelle für Phoenix, USA. Aufgrund der Bedeutung des Gebietes wurde eine Strategie zur Verhütung weiterer Beeinträchtigungen der Wasserqualität ausgearbeitet. Diese beinhaltete Managementaspekte zur Gewährleistung einer schnellen Planung und Ausführung der notwendigen Arbeiten gekoppelt mit der Planung, dem Bau und dem Betrieb von Rückhalte und Umleitungssystemen für auftretende Wässer. Die Auslegung dieser Systeme erfolgte auf der Grundlage der Daten des Einzugsgebietes und der klimatischen Verhältnisse, wobei verschiedene Wahrscheinlichkeiten der Überschreitung der ermittelten Werte berücksichtigt wurden. Innerhalb von acht Monaten konnten die Tailings aus dem betroffenen Gebiet entfernt werden, ohne dass belastete Oberflächenwässer freigesetzt wurden.